Sasha CampbellThose tiny pests that look like small bumps on your plants may be scale insects.
They feed by sucking sap from plants. This can weaken plants, causing yellow leaves, poor growth, wilting, and even branch dieback if the infestation is severe.
So, it’s important to control them early.
Identification
Scale insects belong to the insect order Hemiptera and the superfamily Coccoidea [1]. They can cause serious damage to the garden, greenhouse, and houseplants, depending on the extent of the infestation.
Both armored scale and soft scale insects can affect indoor plants, fruit trees, and ornamentals.
These pests look like tiny shell-like bumps on stems, branches, or leaves. Many scale insects, especially soft scales, excrete a sticky substance called honeydew, which can lead to black sooty mold growth on plants.
Depending on the species, scale insects may appear white, brown, gray, or black. Brown scale insects are among the most common types found on garden plants and trees.
Signs of Scale Infestation
- Sticky leaves or honeydew.
- Ants crawling on plants.
- Black sooty mold.
- Tiny bumps on stems or leaves.
- Yellow leaves.
- Poor plant growth.
- Leaves dropping early.
How to Get Rid of Scale on Plants Naturally
Below are some common home remedies and natural solutions that you can try.
Tip: Most sprays work best against young scale insects called crawlers. Adult scales have a hard covering that protects them from many treatments. For the best results, repeat sprays every 7 to 10 days until no new crawlers appear.
1. Rub Them Off
If the problem is small, this is one of the cheapest ways to control scale insects. This method works well for small infestations on houseplants.
An old toothbrush is a good tool for scraping or rubbing the pests off the stems.
Alternatively, a cotton swab dipped in rubbing alcohol and pressed directly onto each scale insect should do the trick. However, test rubbing alcohol on a small part of the plant first, as some plants may be sensitive to it.
Also, check under leaves where they may be hiding. Afterward, you can use horticultural oil or insecticidal soap to help control any remaining pests.
2. Horticultural Oil
Some gardeners make homemade horticultural oil sprays using vegetable oil and liquid soap. However, commercial horticultural oils are usually safer because they are specially formulated for plants.
If you decide to make your own spray, test it on a small area first.
To make a homemade horticultural oil spray, first mix 1 cup of vegetable oil with 1 tablespoon of liquid soap. Then combine 1 tablespoon of this concentrate with 1 cup of water before spraying.
Avoid spraying during very hot weather or strong sunlight. Also, use pure liquid castile soap instead of dish detergent when possible.
Finally, shake well and coat the affected plants with your homemade scale spray. Use the measurement as a guide for larger portions.
3. Pruning
Pruning is a useful way to remove heavily infested branches and plant parts.
If you act quickly, pruning can prevent pests from spreading to other parts of the plant. Also, there will be no honeydew to attract other pests.
Afterward, dispose of heavily infested plant parts in the trash or remove them from the garden area. Pruning may also strengthen plants and help them resist further damage.
Sterilize pruning tools afterward if moving between plants.
4. Beneficial Insects
Using beneficial insects is one of the main biological methods for controlling scale infestations. Lady beetles, lacewings, and tiny parasitic wasps are natural enemies that can help reduce scale insect populations [2].
You can also purchase some of these beneficial insects at various garden centers or online.
It is also possible to encourage them to visit your garden. Plant flowers like yarrow and cosmos to attract them.
5. Neem Oil
Neem comes from the seeds of the neem tree. Gardeners and farmers have used neem oil for many years as a natural pest control product.
Mix 2 teaspoons of liquid soap with 2 tablespoons of neem oil and 1 gallon of warm water to treat scale insects. Finally, shake well and spray the solution on the affected plants.
You can also find this natural treatment in concentrate form. It comes mixed with other active ingredients in organic commercial sprays.
Neem oil can help control scale insects by interfering with feeding, growth, and development. The oil may also smother some insects.
Spray in the early morning or evening to avoid leaf burn and protect pollinators.
6. Insecticidal Soap
Insecticidal soap is another natural option for controlling soft scale insects. You can make a simple homemade spray using pure liquid castile soap, water, and vegetable oil.
Mix 2 tablespoons pure liquid castile soap, 1 tablespoon vegetable oil, and 1 gallon of water.
Finally, spray the DIY scale-infestation spray on the affected plants. You can also purchase commercially available insecticidal soap.
7. Bug Blaster
This method uses a strong blast of water to remove scale insects from plants.
The apparatus consists of a ‘wand’ and a nozzle. It is designed to dislodge soft-bodied pests from plants using a strong stream of water without harming most established plants.
Bug Blaster uses a focused stream of water, which helps remove pests while using less water than some spray methods. However, if the pests return, repeat the process.
Water sprays work best on young scale crawlers and light infestations.
8. Azadirachtin
Azadirachtin is a commonly used organic insecticide for controlling scale insects on plants. It stops insects from feeding, growing, and reproducing.
When used properly, azadirachtin is generally considered less harmful to many beneficial insects and mammals than synthetic pesticides.
9. Essentria IC-3
This commercial product controls many pests.
Essentria IC-3 contains a blend of essential oils and other ingredients. It is a multipurpose natural insecticide containing rosemary oil, peppermint oil, and geraniol.
This plant-scale treatment can be used for spraying or misting, as directed by the manufacturer. It can also be used for other pest-control purposes, according to the manufacturer’s instructions.
Essentria IC-3 may help control some scale insects on plants. It also works against many other crawling and flying insect pests.
10. Diatomaceous Earth (DE)
DE may help control young crawling scale insects.
Diatomaceous earth damages the protective outer layer of soft-bodied insects, leading to dehydration and death. However, it is generally less effective against mature scales protected by hard coverings.
Use only food-grade diatomaceous earth on plants. Dust it lightly on stems and leaves where young crawlers are active. Reapply after rain or watering because wet DE loses its effectiveness.
How to Prevent Scale Insects
- Inspect new plants before bringing them home.
- Avoid overfertilizing plants.
- Prune weak or crowded growth.
- Encourage beneficial insects.
- Keep plants healthy and stress-free.
- Avoid bringing home plants with visible bumps or sticky leaves.
- Keep ants under control because they protect soft scale insects from beneficial insects.
- Avoid overwatering, as stressed plants are more likely to suffer from pest problems.
Frequently Asked Questions
Will Dawn dish soap kill scale?
Dawn dish soap may help control some soft scale insects. However, detergents may damage sensitive plants.
A true insecticidal soap or pure liquid castile soap is usually safer.
What causes scale insects on plants?
Scale insects often appear on stressed or weakened plants. They may spread from nearby infested plants or from new plants brought into the garden or home.
They can also spread through wind-blown crawlers, insects, animals, or contact with infested plant material. Warm, sheltered conditions can also help them multiply quickly.
Can a plant recover from scale insects?
Yes, many plants can recover if the infestation is treated early. Pruning damaged areas and using natural treatments may help restore plant health.
Are scale insects harmful to humans?
Scale insects do not bite or harm humans. They are only a problem for plants.
What plants do scale insects attack?
Scale insects attack many plants, including houseplants, citrus trees, fruit trees, shrubs, hibiscus, camellias, ornamentals, and some vegetables.
Does neem oil kill scale insects?
Yes, neem oil may help control scale insects. It works by interfering with their feeding, growth, and development.
The oil may also smother some insects. Repeated applications are often necessary.
What is the fastest way to get rid of scale on plants?
For light infestations, scraping or rubbing them off by hand gives the quickest visible results. Heavy infestations may require pruning along with repeated sprays of horticultural oil or insecticidal soap.
Takeaway
Scale insects can make plants look unhealthy and weak. The pests may affect houseplants, garden flowers, shrubs, fruit trees, and vegetable crops.
Use the natural methods above to control scale insects, prevent future infestations, and help your plants stay healthy.
I have hard scale insects on my water lilies in the koi pond. They are on the lily pads and stems. How did this happen and how to get rid of them?